58 HEAD AND NECK 



scapula. The lower fibres ascend, and terminate in a small 

 triangular tendon which plays over the smooth triangle at the 

 root of the scapular spine, and which is inserted partly into the 

 lower lip and partly into the upper lip of the spine. The muscle 

 is supplied by the accessory and the third and fourth cervical 

 nerves. It draws the scapula medially and braces the shoulder 

 backwards, raises the tip of the shoulder, or depresses the 

 scapula and turns the glenoid fossa upwards, according to 

 whether the middle, the upper, or the lower fibres are mainly 

 in action. 



Dissection. On the second day after the subject has been 

 placed on its face, the dissector, in conjunction with the dissector 

 of the superior extremity, must reflect the trapezius muscle. 

 First separate the muscle from the occipital bone, and then divide 

 it about half an inch from the spines of the vertebrae. The 

 muscle can now be raised and thrown laterally towards its 

 insertion. On its deep surface the accessory nerve, the twigs of 

 supply from the third and fourth cervical nerves and the ascend- 

 ing branch of the transverse cervical artery will be noticed. It 

 is the duty of the dissector of the upper limb to dissect the 

 structures mentioned, but the dissector of the head and neck 

 should trace the artery to its origin from the transverse cervical 

 artery. 



The attachments of the levator scapulas also must be defined. 

 Two twigs from the third and fourth cervical nerves, which lie 

 on its surface and finally enter its substance, have already been 

 secured. Further, passing downwards under cover of the 

 levator scapulae muscle, the dorsal scapular nerve (O.T. nerve 

 to the rhomboids) and the descending branch (O.T. posterior 

 scapular) of the transverse cervical artery will be found. Almost 

 invariably the dorsal scapular nerve gives one or two twigs to 

 the levator scapulas. 



The levator scapulae, the rhomboids, the posterior serrati and 

 the splenius are classed as muscles of the second layer. The 

 rhomboids and the lower part of the levator belong to the dis- 

 sector of the arm ; the remaining muscles are the property of 

 the dissector of the head and neck. 



Musculus Levator Scapulae. The levator scapulae arises by 

 four slips from the posterior parts of the transverse processes 

 of the upper four cervical vertebrae. The slips unite to form 

 an elongated muscle which extends downwards and backwards 

 to be inserted into that portion of the vertebral border of the 

 scapula which is placed above the level of the spine. Its 

 nerve-supply is derived from the third and fourth cervical 

 nerves, and also from the dorsal scapular nerve. The muscle 

 raises the scapula and draws it towards the vertebral column. 



The origin of the posterior belly of the omo-hyoid muscle 

 may now be examined. It is attached to the upper transverse 



